Projection system

ABSTRACT

Improved electronic projection systems having a container with a conducting interior and a deformable medium in the container which decreases in resistivity with decreases in thickness in the presence of electrical charge on the surface of the medium are provided by using as the deformable medium the polymeric reaction product of benzyl alcohol and aromatic hydrocarbons using as a catalyst an acidic material.

United States Patent 1191 Timberlake Sept. 25, 1973 54 l PROJECTION SYSTEM OTHER PUBLICATIONS [75 Inventor: Charles T'mberlake Syracuse Olah, Friedel-Crafts and Related Reactions, Vol. II, Pt. 1, Interscience Pub. New York (1964) pp. 494, 553, [73] Assignee: General Electric Company, 559 &

Syracuse, N Y Olah, Friedel-Crafts and Related Reactions, Vol. I, In- Filed. Nov 23 1970 terscience Pub. New York (1964) p. 9.

[21] Appl. No.: 92,178 Primary ExaminerCurtis R. Davis Attorney-W. J. Shanley, Jr., Frank L. Neuhauser, 05- Related Apphcauon Dam car B. Waddell, Marvin Snyder and Joseph B. Forman [63] Continuation of Ser. No. 766,880, Oct. 11, 1968,

abandmed" 57 ABSTRACT 52 US. Cl. 178/75 1), l78/7.87, 260/668 c Improved electronic projection system having a 51 Int. Cl. H0411 3/16 tainfir with a conducting interior and a deformable [58] Field of Search 260/668 (3; dium in the container which decreases in resistivity 178/75 D with decreases in thickness in the presence of electrical charge on the surface of the medium are provided by 5 References Cited using as the deformable medium the polymeric reac- UNITED STATES PATENTS tion product of benzyl alcohol and aromatic hydrocarbons using as a catalyst an acidic material. 3,288,927 11/1966 Plump l78/7.87 3,109,868 11/1963 Fields et a1 260/668 C 9 Claims, 2 Drawing Figures PROJECTION SYSTEM This application is a continuation of Ser. No. 766,880, filed Oct. 11, 1968, and now abandoned.

PROJECTION SYSTEM This invention relates to projection systems of the electronic type. More particularly, it relates to such projection systems having a container with a conducting interior and a deformable medium in the container that decreases in resistivity with decreases in thickness in the medium, the medium being the polymeric reaction product of benzyl alcohol and aromatic hydrocarbons.

There is described in U.S. Pat. No. 2,943,147, June 28, 1960, assigned to the same assignee as the present invention, a projection. system of the above type employing a deformable medium having a high resistivity which is responsive to a velocity modulated electron beam. Generally speaking, this projection system, which is illustrated in FIG. 1 of the drawing, comprises an evacuated glass envelope containing an electron gun 11 for producing an electron beam 13 and deflecting it in a rectangular raster over the surface of a light transmitting deformable medium 15 which is within a portion 17 of the transparent container. An enlarged view of this portion of the assembly is shown in FIG. 2. The beam 13 is preferably velocity-modulated by a television signal applied to the deflection means (not shown) in the electron gun ll. Deformable medium 15 has a central portion 19 of decreased thickness which is conincident with the raster area produced by electrons from beam 13 attracted to a conducting coating 21 on the inner surface of the container portion 17. These same electrons produce deformations in the surface of the deformable medium 15 and the amplitudes of these deformations are a function of the number of electrons deposited by the beam 13 at the various points on the surface of medium 15. Thus, the amplitudes of these deformations are a function of the modulated electron beam 13.

The deformations on the surface of medium 15 are utilized to diffract light from a source 23 in an optical system including a lens 24 which projects an image of light source 23 on the surface of medium 15 through a bar and slit system 25. Another lens 29 images the slits of system on the bars of another bar and slit system 31 if there are no deformations on the surface of deformable medium 15. However, any deformations on such surface diffract the transient light so that it passes through the slits in the system 31 with an intensity that corresponds to the amplitudes of the deformations and hence the amplitudes of the applied modulating signal such as a television signal. The light passing through lens 29 is imaged by a projection lens 33 on screen 35 by means of mirror 37.

Ifa conventional deformable medium is utilized at 15 in the illustrated system, the average charge density produces a force on the medium 15 that overcomes the surface tension from the excess medium outside the raster area and decreases the portion 19 of medium 15 to zero thickness. Under such conditions, no deformations can be formed and the system becomes inoperative until the medium is replaced. The above patent teaches that if the medium has the property of decreasing in resistivity with decreasing thickness, portion 19 does not decrease to zero thickness under the pressure of the charges but maintains a thickness which is a function of the magnitude of charge density on the surface of the medium 15. With decrease in resistivity, the time constant is decreased for the passage of leakage current from the surface of deformable medium 15 to the conducting coating beneath it. This results in an increase in leakage current, decreasing the charge density on the surface of the medium 15 and somewhat relieving the pressure. Eventually, an equilibrium condition is reached in which the pressure from the charges on the surface of the medium equals the pressure from the surface tension on the excess medium surrounding the raster at which the thickness at this equilibrium condition is maintained. The charge density on the surface of the medium never decreases to zero because of such leakage because it is continually being replaced by electrons from beam 13. Y

The deformable compositions described in the aforesaid patent, U.S. Pat. No. 2,943,147, as suitable for the medium are required to be transparent, be capable of withstanding electron bombardment without significant decomposition, have a viscosity at the operating temperature (between about 25 and 150 C) of approximately to 50,000 centistokes, and the deformable composition must not decompose the conducting coating. The medium must also have a volume resistivity that varies within the range of approximately 10 to l0 ohms-cm., with the average resistivity at the stable thickness being approximately 10 ohms-cm.

Among the deformable media or fluids described in the above patent are beeswax, methyl silicone fluids, methyl silicone fluids containing up to five percent of phenyl silicones, methylphenyl silicones containing an average of two methyl and phenyl groups per silicon atom in which the mole ratio of methyl groups to silicon atoms is greater than zero and less than two, etcf However, it has been found that these deformable fluids are not as stable as one would desire because under the influence of an electron beam, the deformable medium or deformable fluids tend to increase in viscosity and with continued use in the projection system described above, the viscosity increases to a point where gel particles begin to form and the deformable medium ultimately gels. It is quite obvious that the apparatus can no longer be used with a gelled medium which will not suitably decrease in thickness.

The shortcomings of the above media were alleviated by providing typically very specific Friedel-crafts reaction produces of benzyl chloride and aromatic materials such as biphenyl, naphthalene, toluene and benzene, including substituted materials of these types. Typical such projection systems are described, for example, in U.S. Pat. No. 3,317,664 relating to media which are the reaction product of benzyl chloride and naphthalene and in U.S. Pat. No. 3,317,665 relating to the Friedel-Crafts reaction product of benzyl chloride and biphenyl material and in U.S. Pat. No. 3,288,927 relating to such reaction products of benzyl chloride and benzene, toluene, etc., the above patents being assigned to the same assignee as the present invention.

While material provided by the teaching of the immediately preceding patents had a desirable long lived suitable viscosity, it was found that under continuous electron bombardment under operating conditions, there tended to be formed in the media a substrate which detracted from the acuity of the reproduced writing. With continued use, the substrate develops to the point where the image producing capability of the system is limited.

From the above it will be seen that there is a need for materials which can be used as medium 15 which are not only characterized by long lived and suitable viscosity under the radiation effects of electrons from beam 13 but which at the same time are resistant to substrate formation or the formation of materials within the medium which detract from the writing capability of the medium or may even render the medium entirely useless in this respect. It is, therefore, a principal object of the invention to provide an electronic projection system employing, as deformable media, materials which are possessed of desirable and long lived viscosity under irradiation and which, under such irradiation, are resistant to the formation therein of substrates or products which detract from their usefulness in producing images.

It has been unexpectedly found that certain polymeric reaction products of benzyl alcohol with aromatic hydrocarbons using acidic material as a catalyst fulfill the above characteristics and provide a deformable medium which is possessed of long working life and other advantageous qualities along with resistance to the formation under working conditions of substrates or inclusions which detract from their image producing capability.

Those features of the invention which are believed to be patentable are set forth with particularity in the claims appended hereto. The invention will, however, be better understood and further objects and advantages thereof appreciated from a consideration of the following description and the drawing in which FIG. 1 is a schematic representation of the present projection system including medium 15 and FIG. 2 is a detailed representation of medium 15 in its immediate surroundings.

While benzyl alcohol is the preferred hydroxyl containing material used herein, other related materials can be used including alkyl and aromatic-substituted benzyl alcohol such as the methyl and benzyl, phenyl and naphthyl substituted materials, among others.

The aromatic hydrocarbons which can be substituted or unsubstituted which have been found useful according to the present invention include benzene, toluene, xylene, naphthalene, tetralin, dihydroanthracene, phenanthrene, biphenyl, terphenyl, cyclohexylbenzene, ethyl benzene, propyl benzene, t-bu'tylbenzene, benzyl toluene, diphenylmethane, and others which will occur to those skilled in the art. Blends of the above materials can also be used.

A preferred condensation catalyst used in connection with the present invention is polyphosphoric acid. Other acidic materials which are useful including sulfuric acid, para-toluene sulfonic acid, phosphoric acid, phosphorus pentoxide, hydrogen fluoride, alkane sulfuric acids, such as methyl, ethyl, etc. acidic cation exchange resins illustrated by Dowex 50, a sulfonated styrene divinyl benzene and Amberlite lR-100 or sulfonated phenol formaldehyde, and others which will occur to those skilled in the art. Also useful is a synthetic Fullers earth material known as Celkate which contains adsorbed sulfuric or phosphoric acid, Celkate being a synthetic magnesium silicate material made by the Johns-Manville Corporation.

Generally speaking, in forming the present medium materials preferably from about 1.0 to 4.0 moles of benzyl alcohol are used for each mole of aromatic hydrocarbon. Broadly speaking, from about 0.1 to about 10 moles of benzyl alcohol or related material are used for each mole of aromatic hydrocarbon.

While the amount of condensation catalyst required to effect the desired reaction between benzyl alcohol and toluene will vary with the activity of a particular catalyst system, a useful mole percent range for polyphosphoric and sulfuric acids, the preferred catalysts of this invention, is from 0.1 to 10 mole percent per mole of benzyl alcohol with a preferred range of 0.8 to 1.2 mole percent of the benzyl alcohol. Those skilled in the art will be able readily to determine the effective amounts of other catalysts of the type prescribed herein.

The following examples illustrate the practice of the present invention, it being realized that they are to be taken as exemplary only and not limiting in any way.

EXAMPLE 1 A flask fitted with stirrer, thermometer, gas inlet tube and constant volume dropping funnel was purged with nitrogen, charged with 4,360 g of polyphosphoric acid and heated to C. A mixture of 3,260 cc (32 moles) of benzyl alcohol and 1,060 cc (10 moles) of toluene was added dropwise to the heated polyphosphoric acid with stirring. The temperature tended to rise during the addition and the addition rate along with heating or cooling as indicated was adjusted to maintain a temperature of from about to C, the addition being completed in 4 hours. The mixture was further stirred and heated at 140 to 145 C for another hour and allowed to cool to about 1 15 C to which 3 liters of water were added. Upon separation of the layers, the oil layer was washed with yet another 3 liters of water, the water being separated and discarded. One liter of toluene was added to the oil layer and the solution washed with 500 cc of 20 percent by weight sodium hydroxide solution in water. The oil layer was further washed with water until neutral and then dried with anhydrous potassium carbonate and stirred with Celkate and potassium carbonate, the filter cake was rinsed with toluene and the rinsings added to the oil which was then successively treated with charcoal and then with Celite, a finely divided silica. The Celite-charcoal mixture was then filtered out, rinsed with toluene and the oily fluid distilled to remove toluene. The remaining oily fluid was then distilled to provide fractions as indicated in TABLE 1 below.

TABLE I Pot Frac- Temp. Vapor Temp. Fraction Pressure tion C C g p, Hg 2 133-138 104 (max) 389. 60 to l 3 170-244 51-178 142.9 1 4 227-287 -185 250.8 2.7

The residue remaining in the pot was approximately 2,070 g, this material being transferred to a molecular still and distilled at a temperature of from about 164 to 404 C. This distillation produced about 1,070 g of crude distillate which was further distilled as summarized in TABLE 11 below.

TABLE 11 Pot Over- Temp. Pressure Distillate Viscosity of head C .1., l-lg (grams) Pot Material 1 100-195 14 69.8 490 cs (50C) 2 140-182 10 75.7 639 (50C) This material remaining in the still pot was divided into two portions and treated as follows:

A 323 g aliquot was charged into a one-liter molecular still and 9 grams of material distilled out at 1 18 to 148 C at a vacuum of 1.2 X 10 to 2.2 X 10" Torr. The material remaining in the still had a mass of 220 g, this material then being treated with adsorbent materials including one-half weight percent of Norite, and activated carbon or charcoal, and one-half weight percent of Celite, each being introduced and followed by stirring at 50 C for 1 hour and 1/2 hour respectively. The fluid having been filtered, there was added to the filtrate two weight percent of Celkate followed by stirring for 1 hour at 50 C. The filtrate from the above was treated with one weight percent of Celite with stirring for 1 hour at 50 C and the resulting fluid filtered through a filter of 0.45 micron porosity. The fluid remaining had a weight of about 200g and a viscosity of 813 cs at 50 C. This material was useful as a writing material and as shown hereinafter was particularly resistant to the formation of deleterious substrate material.

The fluid remaining after that withdrawn above 323 g aliquot was distilled as shown in TABLE III below:

TABLE III Pot Over Temp. Pressure Distillate Pot Viscosity head C 1.1., Hg (grams) cs (Temp.)

3 178-322 10 504 Resin, high viscosity The 504 g product had a viscosity of 1,048 cs at 50 C and was useful as a writing material.

EXAMPLE 2 Example 1 was repeated except that a 20 percent potassium hydroxide solution was used as the alkaline wash along with a 20 percent solution of sodium sulfate to remove the alkali. The fluid remaining was distilled as shown in TABLE IV below:

TABLE IV Pot Vapor Frac- Temp. Temp. Pressure Distillate tion C u, Hg Mass (g) 1 to 209 to 110 atm. Not weighted max. 2 to 200 10-15 mm 3 106-198 68-91 42-10 412 4 183-248 61-174 4-10 192 5 240-288 156-185 -28 150 The remaining 1,820 g of material was distilled in a molecular still at between 175 C and 379 C at a vacuum of 1 to 290 microns to produce 876 g of crude product having a viscosity of 390 csat 50 C. This material was further distilled as summarized in TABLE V below:

TABLE V Pot Over Temp. Pressure Distillate head "C u, Hg Mass (5) Remarks 1 120-195 30 to 9 91 Pet viscosity is 541cs at 51.1"C 2 172-173 -10" 93 Pot viscosity 911 cs at 50C Mass 660 g Refractive index 1.6323 at 25C The 660 g residue remaining after the above distillation had a vapor pressure of 3.5 X 10 Torr. at 50 C as measured by the effusion technique. After adsorbent treatment in a manner similar to that of Example 1, the remaining fluid had a weight of 600 g, the viscosity being 911 cs at 50 C.

EXAMPLE 3 Example 2 was repeated to give a 768 g of final product having a viscosity of 868 cs at 50 C, a vapor pressure of 2.3 X 10 Torr. at 50 C and 9.0 X 10 Torr. at 25 C, the refractive index being 1.6320 at 25 C. This material was useful as an image-producing medium.

EXAMPLE 4 Example 2 was repeated in all respects except as to the molecular distillation. In the present instance only about 60 to percent of the quantity of distillate normally taken was used to prepare the final fluid. Accordingly, the equivalent pot residue, remaining after the distillation of the five higher volatility fractions of Example 2, was molecularly distilled to give 603.8 g of material as set forth in TABLE VI below:

TABLE VI Pot Vapor Frac- Temp. Temp. Pressure Weight tion C C u, Hg (grams) 1 to 200 atm. 664 2 131-200 45 10-15 66 3 -196 95-100 ca. 80 382.3 4 199-228 81-192 ca. 14 325.4 5 153-271 4 to 3 603,8

Stripping and slurry treatment of fraction 5 in a'manner similar to that of the previous examples gave a final product having a weight of 347 g, a refractive index of 1.6281, a viscosity at 40 C of 1,065 cs, a vapor pressure of 3.5 X 10 Torr. at 50 C and 1.0 X 10 Torr. at 25 C. This material was useful as a writing fluid.

EXAMPLE 5 This example illustrates the practice of the present invention using a molar ratio of 1.6 moles of benzyl alcohol to 1 mole of toluene. There was prepared in the manner of Example 11 a material using 1,415 g (15.4 moles) toluene, 2,657 g (24.8 moles) benzyl alcohol and 1,120 g of polyphosphoric acid. After removal of the acidic impurities in accordance with the previous Fractions 6 and 7 were found to provide useful writing fluids in connection with the present invention.

EXAMPLE 6 This example shows the preparation of a useful toluene derived writing fluid using a ratio of approximately 4 moles of benzyl alcohol to one mole of toluene. The procedure of Example was repeated using 355 g (3.9

175 C. After removal of acidic impurities, the material was distilled as set forth in TABLE X below:

moles) toluene, 1,660 g (15.4 moles) benzyl alcohol TABLE X and 2,337 g of polyphosphoric acid. After removal of 5 H V isw i h acidic impurities, the material was distilled as shown in i Bmlng Range aefmcnle t t C [-1 l d 25 C es at rams) TABLE VI. 1011 (mm g) 11 ex 50 C g 1 189-200 (15) 1.5685 1.0 2 154-200 (0.01) 1.5733 177.0 3 200-250 (0.01) 1.5930 37.0 TABLE VH1 4 250-290 0.01) 1.6031 143.5 5 97-133 (10) (Solid) 32.4 6 94-118 (10 1.6179 56 21.6 7 125-130(10 1.6174 60 21.1 8 130 10- 1.6295 395 370.0 Frac- Borlmg Range Refractive cosity Weight p Residue 7415 tion "C (mm Hg) lndex, 25C cs at (grams) 50C 1 42-200 (30) 1.5626 67.7 5 Fraction 8 was found to be part1cularly useful as a writ- 2 100-200 (0.1) 1.5731 142.6 m fl id 3 200-250 (0.1) 1.5992 64.0 4 250-290 (0.1) 1.6026 101.7 EXAMPLE 9 5 110-125 (10) 1.6185 43 26.1 s 1 15-125 10- 173 56 This example illustrates the preparat1on accordmg to 7 125 (10") 1-6283 395 356-0 the present invention of a naphthalene-derived mate- Pot ResIdue 825.8

rial. A nitrogen-filled, three-neck flask equipped with stirrer, gas inlet, theremometer and dropping funnel, was charged with 1,652 g of polyphosphoric acid which Fraction 7 of the above table was found to be useful as was heated to a temperature of C A Solution of a wmmg fund 1,031.6 g (8.06 moles) of naphthalene and 1,237 cc, 1,298 g (12 moles) of benzyl alcohol at a temperature 0 4 EXAMPLE 7 of about 120 C was added to the polyphosphonc ac1d in a slow stream over a per1od of about 2 hours. The temperature of the flask contents rose to a temperature This example illustrates the preparation of a toluenef b t 155 C t the completion of the addition and derived material using a ratio of approximately 3.2 was i t i d t a t m rature of about 150 C for 1 moles of benzyl alcohol to each mole of toluene, carryhour, cooled to approximately 50 C and mixed with 1 ing out t e re ction at a temperature of 5 C as pliter of water. The acid layer was separated and the orposed t a t mp ratur f l 0l C for Ex p 5 ganic phase treated in a manner similar to that deand 6. There were used as the reactants 449 g (4.88 35 ib d i Ex m le 1. The material was distilled as moles) toluene, 1,660 g b zy 81601101 summarized in TABLE XI below, the third and subseand 2.133 g p y/ph ph acid- After removal of quent fractional distillations being carried out with a acidic impurities. a distillation was carried out as in molecular still. The final product was suitable as a writ- TABLE 1X below: ing fluid.

TABLE XI Pot Vapor temp., temp., Mass Fraction PC C. Presure (grams) Remarks 7 90-221 Atmos Chiefly unreacted naphthalene and toluene solvent.

. 194-275 Water aspirat0r 409 37:75 Hg 560 Cnlde product. Viscosity is 973.4 cs. at C. @;;:*"':i 52. 5 Represents stripping out of volatile: from crude product. Bmk distmmn-fl- "ii. 2 i i(i- 'E6EEIIIIIIi 1?? ii'r ii 0 95m:

TABLE IX EXAMPLE 10 Vis- Frac- Boiling Range Refractive cosity Weight tion C (mm Hg) lndex, 25C 6826 (grams) 5Q I 37400 Us) 15693 2256 Th1s example illustrates the preparation of a writing 2 130-200 (.04) 1.6002 4 ,0 fluld usmg xylene as a precursor. To 3,525 g of polyi 3338 33 128;? 5-8 phosphoric acid at 90 under dry nitrogen there was 5 1094 5 gm"; (S'ofid) added, from separate addition funnels, 1,388 g (12.85 6 129433 (1 0- 1.6170 55 16.6 moles) benzyl alcohol and 425.5 g (4 moles) p-xylene g Residue 133 "6278 3117 ,28 such that approximately two drops of the alcohol were added for each drop of p-xylene. The addition was carried out over a 5 hour period at a temperature of about 1 10 C. The cooled reaction mixture was hydrolyzed with water and the organic layer washed twice with water, 10% sodium hydroxide solution and again with water until the aqueous extracts were neutral. 1 liter of benzene was added during the washing procedure to reduce the viscosity of the organic phase. Removal of solvents and light ends and isolation of the product fluid from the organic phase was accomplished by distillation according to TABLE XII below.

TABLE XII Fraction Boiling Range Pressure Amount No. C

187-50-1 85-155 -20 mm Hg 10 g 187-50-2 150-235 0.4 mm 171.7 g

187-51-1 150-200 2X10" mrn 241.3 g

187-51-2 262-276 4X10 min 246.5 g

(Crude product) 187-51-3 611.5g (residue) The product of the above distillation was redistilled according to the procedure shown in TABLE XIII below, the residue being suitable as a writing fluid and having a viscosity of 1,000 cs at 46 C and a refractive index of 1.6237 at 25 C.

TABLE XIII Fraction Boiling Range Pressure Amount 187-55 126 1.8)(10' mm 35 g 187-56-1 217-21 8X10 mm 138.62 g

Product 187-56-2 31.44 g (residue) EXAMPLE 11 This example illustrates the use of the sulfuric acid as a condensing agent for naphthalene based material. To a rapidly stirred slurry of 1,025 g (8 moles) naphthalene, 1,300 g (12 moles) benzyl alcohol, and 1,500 cc cyclohexane cooled to 10 C there was gradually added over a 1.1 hour, 1,000 cc of concentrated sulfuric acid, the temperature being maintained between C and 75 C. Stirring was continued for an additional 1/2 hour at 5 C and the organic layer separated. The cloudy organic phase was first stirred with Celkate and filtered, diluted with one liter of benzene, again stirred with Celkate and filtered to give a clear filtrate. Benzene, cyclohexane, naphthalene and light ends were removed by distillation as above and 797 g of crude productsisolated by distillation over a 147 to 300 C range, this material having a viscosity of 587.6 cs at 49.8 C and a refractive index of 1.6532. This material was stripped and distilled to provide a final product having a weight of 331 g, a boiling range of from about 133 to 232 C at 2 microns of mercury, a refractive index of 1.6545 at 24 C, a viscosity of 1,200 cs at 50.2 C. This material served as a useful writing fluid.

EXAMPLE 12 Example 11 was repeated on a larger scale using 2,050 g (16 moles) naphthalene, 2,600 g (24 moles) benzyl alcohol, 4 liters cyclohexane and 2,000 cc concentrated sulfuric acid. There was provided 1,694 g of a final fluid having a boiling range of 134 to 245 C at 4 microns Hg, a viscosity of 1,215 cs at 49.8 C and a vapor pressure of 2.5X Torr. at 50 C. This material was useful as a writing fluid.

EXAMPLE 13 This example illustrates the preparation of the present materials using benzene as a precursor material. To 1,308 g (3.9 moles) of polyphosphoric acid at 80 C, there was added a mixture of 234.3 g (3 moles) of benzene and 810.8 g (7.5 moles) of benzyl alcohol over a period of about 1.7 hours, the reaction temperature being maintained at from about to C. The resulting mixture was cooled to 80 C and one liter of water added slowly to maintain the temperature below 95 C. After cooling to below 80 C, 1 liter of benzene was added with stirring over a period of several minutes. The organic material was separated from the acid and washed with 500 cc of a sodium sulfate-potassium hydroxide water solution. The slightly basic material was then washed with 500 cc of a saturated sodium sulfate-water solution until neutral and filtered. The organic layer was collected, slurried with Celkate and filtered, benzene and light ends being removed by atmospheric and vacuum distillations as taught above. The 123.5 g product collected by vacuum distillation was distilled at a temperature of 220 to 350 C at a pressure of 10' to 10 Torr., the final material having a refractive index of 1.6402 at 25 C and a viscosity of 2563.6 cs at 502 C. This material provided a useful writing medium.

EXAMPLE 14 This example illustrates the preparation of the present materials using tetralin as a precursor material.

To a hot, 80 C mixture of 396.6 g (3.0 moles) of tetralin and 1,308 g of polyphosphoric acid were added 810.8 g (7.5 moles) of benzyl alcohol. The addition took 2.0 hours and was adjusted to maintain a reaction temperature of 8590 C. After 1/2 hour additional stirring, 1,500 ml of water were added and stirring continued for another 20 minutes.

The acid layer was drawn off and the organic layer diluted with about 2 liters of benzene. The organic layer was washed twice with 600 ml portion of Na SO H O solutions. It was then washed with aqueous KOH until slightly basic, and finally extracted four times with 600 ml portions of Na SO -H O solutions.

The organic material was then collected, slurried with Celkate for about l/2 hour, and filtered. Benzene, residual tetralin, and light ends were removed by atmospheric and vacuum distillations. The crude product, 345.8 g, was also collected by distillation.

From this crude product, a final product, 186-3-5B, was isolated by stripping and distillation. Sample 186- 3-58 was slurried with Celkate and filtered through Whatman paper and Millipore filters. The filtered material provided a satisfactory writing fluid.

EXAMPLE 15 A 2 liter flask fitted with a mechanical stirrer, nitrogen inlet tube, thermometer, addition funnel, and reflux condenser was charged with 460 g of polyphosphoric acid and 180 g (1 mole) of 9,10- dihydroanthracene. The mixture was heated to 1 10 C to melt the dihydroanthracene.

To this mixture were added 324 g (3 moles) of benzyl alcohol dropwise with stirring. The temperature rose during the addition and the addition rate and/or heating and cooling was adjusted to maintain a temperature between and C. The addition was complete in 45 minutes. The mixture was heated and stirred at 120 to 130 C for another 3 hours before cooling. When the mixture cooled to room temperature, 200 ml of methanol were added with stirring, and the temperature rose to about 55 C. The mixture was then allowed to stir for about 1/2 hour.

The solvents, benzene and methanol, were distilled off at atmospheric pressure to a pot temperature of 123 C. The residual solvent was distilled off under water aspirator vacuum to a pot temperature of 177 C.

The fluid was then distilled with a mechanical vacuum pump and a diffusion pump as summarized in TABLE XIV below:

TABLE XIV Pot Temp. Pressure Weight Fraction "C (Torr. (grams) 1 189-193 2.7X10 58.3 2 176-214 1.0X10 59.2 3 l68-240 98.0

Fractions 2 and 3 were recombined and distilled as summarized in TABLE XV below:

TABLE XV Pot Temp. Pressure Weight Fraction C (Torn) (grams) 1' Ill-I67 l 37.4 10 66.5

Fraction 2 had a refractive index of 1.6482 at 25 C and a viscosity of 970 centistokes at 50 C. This material had a vapor pressure of 5.5X Torr. at 50 C and 1X10 Torr. at 25 C and served as a good writing medium.

EXAMPLE [6 washings 1 to 3 were collected. They contained the acid and methanol washings.

The orange oil was transferred to a still and the solvent distilled off at atmospheric pressure'to a pot tem perature of 125 C. Residual solvent was pulled off under aspirator vacuum to a pot temperature of 125 C. Residual 9,10-dihydroanthracene, Fr fl, was collected on the cold finger by sublimation under rough pump vacuum at 5X10 to 3X10 Torr. to a pot temperature of 118 C.

The fluid was then distilled with a mechanical vacuum pump and a diffusion pump as summarized in TABLE XVI below:

TABLE XVI Pot Temp. Pressure Weight Fraction "C Torr. (grams) 5 120-169 4X10 90.3 Ill 10 1 90 Fraction 6 was redi s tilled and stripped giving 80 grams of material with a viscosity ofliz o csat 50 C and a refractive index of 1.6434 at 25 C. This fluid was found to be extremely resistant to substrate formation.

Samples of certain of the materials of the above examples as set forth in TABLE XVII below were tested for resistance to substrate formation by placing them on a segmented disk and bombarding with irradiation from an 8 KV source. Also tested in this manner was a sample of a typical material prepared according to US. Pat. No. 3,288,927 by reacting benzyl chloride and toluene in the presence of aluminum chloride. After bombardment for approximately hours, the segments were washed free of the oil, the substrate, if any, observed, and the loss in light transmission measured, this value being expressed as percent blue transmission loss (BTL). This figure is a measure of the amount of the blue component of white light that is absorbed by the substrate, the ideal situation (for maximum efficiency) being to decrease blue transmission loss to zero. The blue transmission loss is thus a measure of substrate formation. The results of the tests are set forth in detail in TABLE XVII.

TABLE XVII Material Example Designation BTL WM 323 0.41 3 WM 625 0.52 4 WM 685 0.78 5 WM 834 0.70 6 WM 1086 1.01 7 WM 974 0.78 8 WM 908 0.59 10 WM 1109 0.38 16 WM 1117 0.44 From U S 3,288,927 WM 526 2.22

From the above table it will be readily apparent that the blue transmission loss of the materials of the present invention is far and away less than that of a typical prior art material.

There are provided by the present invention new and improved electronic projection systems as described, the deformable writing medium for which permits operation over long periods of time with little loss in writing ability.

I claim:

1. A projection system comprising a container having a conducting interior, a deformable medium in said container comprising the reaction product of (1) benzyl alcohol and (2) material selected from substituted and unsubstituted aromatic hydrocarbons and mixtures thereof, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating with said conducting interior to subject the medium to a deforming force to produce deformations in the surface of said medium, alight source, and an optical system for projecting light as a function of the deformations in the surface of said medium.

2. A projection system as in claim 1 wherein the reaction product is the reaction product of benzyl alcohol and toluene.

3. A projection system as in claim 1 wherein the reaction product is the reaction product of benzyl alcohol and naphthalene.

4. A projection system as in claim 1 wherein the reaction product is the reaction product of benzyl alcohol and xylene.

5. A projection system as in claim I wherein the reaction product is the reaction product of benzyl alcohol and benzene.

6. A projection system as in claim 1 wherein the reaction product is the reaction product of benzyl alcohol and tetralin.

hydrocarbon material.

9. A projection system as in claim 1 wherein the mole ratio of benzyl alcohol material to aromatic hydrocarbon material ranges from about 1 to 4 moles of benzyl alcohol material for each mole of aromatic hydrocarbon material. 

2. A projection system as in claim 1 wherein the reaction product is the reaction product of benzyl alcohol and toluene.
 3. A projection system as in claim 1 wherein the reaction product is the reaction product of benzyl alcohol and naphthalene.
 4. A projection system as in claim 1 wherein the reaction product is the reaction product of benzyl alcohol and xylene.
 5. A projection system as in claim 1 wherein the reaction product is the reaction product of benzyl alcohol and benzene.
 6. A projection system as in claim 1 wherein the reaction product is the reaction product of benzyl alcohol and tetralin.
 7. A projection system as in claim 1 wherein the reaction product is the reaction product of benzyl alcohol and dihydroanthracene.
 8. A projection system as in claim 1 wherein the mole ratio of benzyl alcohol material to aromatic hydrocarbon material ranges from about 0.1 mole to 10 moles of benzyl alcohol material for each mole of aromatic hydrocarbon material.
 9. A projection system as in claim 1 wherein the mole ratio of benzyl alcohol material to aromatic hydrocarbon material ranges from about 1 to 4 moles of benzyl alcohol material for each mole of aromatic hydrocarbon material. 